A method for extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquid anhydrous

Abstract

The application discloses a kind of based on pure ionic liquid 1,3-butadiene anhydrous extraction rectification method and device in C4 hydrocarbon;The method uses pure ionic liquid as extractant without adding any water or organic diluent, realizes the efficient step-by-step separation of C4 alkanes, butene and 1,3-butadiene by two-stage extraction rectification+ordinary rectification+two-stage pressure reduction flash distillation integrated process under the condition of column still temperature≤80 ℃;Among them, the first extraction rectification column still temperature is 48~53 ℃, and the second extraction rectification column still temperature is 65~80 ℃;Solvent is regenerated by two-stage flash distillation and closed loop circulation;The application fundamentally solves the problems of product purity decline, high energy consumption, easy polymerization and blockage caused by adding water in traditional process, and finally 1,3-butadiene product with purity>99.5% and recovery>99.8% can be obtained, and the comprehensive energy consumption is reduced by more than 30% compared with traditional acetonitrile method.

Description

Technical Field

[0001] This application relates to the field of ionic liquid separation technology, and more specifically, to an anhydrous extractive distillation method for 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids. Background Technology

[0002] 1,3-Butadiene is an important raw material for synthetic rubber and synthetic resins, and its main industrial source is the C4 fraction, a byproduct of ethylene production via steam cracking. This fraction has a complex composition, containing not only 1,3-butadiene but also butane, various butene isomers, alkynes, and small amounts of C3 and C5 components. Because the components have similar boiling points and may form azeotropes, conventional distillation is insufficient for economical and efficient separation. Therefore, extractive distillation is commonly used industrially, which involves adding selective solvents to increase the relative volatility of the components.

[0003] Currently, commonly used extraction solvents include acetonitrile (ACN), dimethylformamide (DMF), and N-methylpyrrolidone (NMP). Among them, NMP is widely used due to its good selectivity and stability, but its process still has some drawbacks: it requires operation at high pressure, resulting in high energy consumption; at the same time, in order to lower the solvent boiling point and inhibit thermal degradation, 8-10 wt% water is often added, which affects product purity, increases the subsequent dehydration load, and further increases energy consumption due to the high specific heat capacity of water; the process involves multiple towers in series and has a complex structure, which prolongs the residence time of materials in the high-temperature zone, easily triggering the thermal polymerization of 1,3-butadiene, leading to equipment blockage and affecting long-term stable operation.

[0004] To address the aforementioned issues, existing technologies have attempted to introduce ionic liquids as extraction components. Patent CN102146012A discloses a butadiene extraction process using a ternary composite solvent of "ionic liquid-acetonitrile-water." While this reduces acetonitrile usage and column temperature to some extent, it still requires the introduction of water and acetonitrile, failing to fundamentally solve the problems of decreased product purity, increased energy consumption, and solvent degradation caused by water. Furthermore, the concentration of the ionic liquid is relatively low, essentially still using acetonitrile as the main solvent, with the ionic liquid used only as an auxiliary agent, failing to fully utilize its advantages of high selectivity and high thermal stability. Patent CN106478341A uses a phenol-water binary mixed solvent to separate butene and butane in C4, but this process still relies on the addition of water. Phenol has a certain degree of toxicity and volatility, which is detrimental to the environment and operational safety, and it does not address the high-purity extraction of 1,3-butadiene.

[0005] In summary, current technologies have not yet developed an extraction process entirely based on pure ionic liquids without the addition of any water or organic additives, nor have they achieved efficient synergy between ionic liquids and the process flow to simultaneously achieve the goals of high product purity, low energy consumption, high solvent stability, and process simplification. Therefore, developing a novel anhydrous extractive distillation process centered on pure ionic liquids and incorporating optimized process structures has significant industrial value and innovative implications. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides an anhydrous extractive distillation method for 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids. The core of this method lies in using a pure ionic liquid (such as imidazole trifluoroacetate or pyridine bis(trifluoromethanesulfonyl)imide salt) without adding any water or organic diluents as the extractant. Through an integrated process of "two-stage extractive distillation + conventional distillation + two-stage depressurization flash evaporation," highly efficient stepwise separation and solvent regeneration of C4 alkanes, butene isomers, and 1,3-butadiene are achieved at significantly reduced reboiler temperatures. This process fundamentally avoids the purity reduction, increased energy consumption, and equipment polymerization blockage problems caused by adding water in traditional processes. Ultimately, it can stably obtain 1,3-butadiene products with a purity higher than 99.5% and a recovery rate higher than 99.8%, while simultaneously achieving efficient regeneration and closed-loop circulation of the ionic liquid. It has the advantages of a simple process, low energy consumption, stable operation, and environmental friendliness.

[0007] In a first aspect, the present invention provides an apparatus for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquid, characterized in that it comprises a first extractive distillation column (1), a second extractive distillation column (2), a distillation column (3), a first solvent recovery tank (4), and a second solvent recovery tank (5) connected in sequence by pipelines. The first extractive distillation column (1) is equipped with an ionic liquid inlet and a C4 hydrocarbon mixture inlet; the top distillation pipeline of the first extractive distillation column (1) is connected to the first condenser (10); the first condenser (10) is equipped with a product collection pipeline and a reflux pipeline to the first extractive distillation column (1); the bottom of the first extractive distillation column (1) is equipped with a solvent-rich outlet pipeline, one of which is connected to the first reboiler (13) and the other is connected to the feed inlet of the second extractive distillation column (2); The second extractive distillation column (2) is provided with an ionic liquid feed inlet and a rich solvent feed inlet from the first extractive distillation column (1); the distillate pipe at the top of the second extractive distillation column (2) is connected to the feed inlet of the distillation column (3) via the second condenser (11); the bottom of the second extractive distillation column (2) is provided with a rich solvent outlet pipe, one of which flows back to the second extractive distillation column (2) via the second reboiler (14), and the other of which is connected to the feed inlet of the first solvent recovery tank (4) via the heater (6); The distillation column (3) has a top distillation line connected to the outlet line and the reflux line returning to the distillation column (3) via the third condenser (12); the bottom of the distillation column (3) has an outlet line, one of which is the product outlet and the other is returned to the distillation column (3) via the third reboiler (15). The top gas phase outlet of the first solvent recovery tank (4) is connected to the first 1,3-butadiene collection pipeline via the fourth condenser (7) and then via the pump (16); the bottom liquid phase outlet of the first solvent recovery tank (4) is connected to the inlet of the second solvent recovery tank (5); The top gas phase outlet of the second solvent recovery tank (5) is connected to the second 1,3-butadiene collection pipeline via the fifth condenser (8) and then via the pump (17); the bottom liquid phase outlet of the second solvent recovery tank (5) is connected to the ionic liquid inlet of the first extractive distillation column (1) and the second extractive distillation column (2) via the pump (18) and then via the sixth condenser (9), forming an ionic liquid closed-loop circulation loop.

[0008] Secondly, the present invention provides a method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids, characterized by comprising the following steps: S1: After the C4 hydrocarbon mixture and ionic liquid are preheated, they are continuously fed into the first extractive distillation column (1) for the first stage of extractive distillation. Alkane products are separated from the top of the first extractive distillation column (1), and 1,3-butadiene is obtained from the bottom of the column. S2: The first rich solvent and ionic liquid obtained from S1 are fed into the second extractive distillation column (2) for a second extractive distillation. The butene mixture is separated from the top of the second extractive distillation column (2), and the second rich solvent rich in 1,3-butadiene is obtained from the bottom of the column. S3: The S2 butene mixture is fed into a distillation column (3) for distillation separation. The light component butene product is collected from the top of the distillation column (3), and the heavy component butene product is collected from the bottom of the column. S4: After heating the second rich solvent, it is sequentially introduced into the first solvent recovery tank (4) and the second solvent recovery tank (5) for two-stage pressure reduction flash evaporation to recover the desorbed 1,3-butadiene. The products are then combined to obtain the 1,3-butadiene product. S5: After the pure ionic liquid after removing 1,3-butadiene from the bottom of the second solvent recovery tank (5) is cooled, it is circulated to the top of the first extractive distillation column (1) and the second extractive distillation tank (2) for reuse.

[0009] Preferably, the ionic liquid is free of water and diluent.

[0010] Preferably, the cation of the ionic liquid is an imidazole or pyridine cation.

[0011] Preferably, the anion of the ionic liquid is trifluoroacetate or bis(trifluoromethanesulfonyl)imide.

[0012] Preferably, the C4 hydrocarbon mixture is preheated to 42°C~45°C; the ionic liquid is preheated to 49°C~50°C.

[0013] Preferably, the first extractive distillation column (1) in S1 has 55 to 90 trays, the C4 hydrocarbon mixture inlet is located in the range of the 30th to 50th tray from the top, and the ionic liquid inlet is located in the range of the 2nd to 4th tray from the top; the top pressure of the first extractive distillation column (1) is set to 0.5 to 0.55 MPa, the top temperature is 45 to 47°C, and the bottom temperature is 48 to 53°C.

[0014] Preferably, the second extractive distillation column (2) in S2 has 60 to 85 trays, the C4 hydrocarbon mixture inlet is located in the range of the 45th to 55th tray from the top, and the ionic liquid inlet is located in the range of the 2nd to 4th tray from the top; the top pressure of the second extractive distillation column (2) is set to 0.5 to 0.55 MPa, the top temperature is 43 to 48°C, and the bottom temperature is 65 to 80°C.

[0015] Preferably, the number of trays in the distillation column (3) in S3 is 80 to 100; the feed inlet of the butene mixture is located in the range of the 60th to 70th tray from the top; the pressure at the top of the distillation column (3) is set to 0.5 to 0.55 MPa, the temperature at the top of the column is 42 to 45°C, and the temperature at the bottom of the column is 51 to 54°C.

[0016] Preferably, in S4, there is a two-stage pressure reduction flash evaporation, with the first flash evaporation pressure being 0.15~0.20 MPa and the second flash evaporation pressure being 0.01~0.05 MPa.

[0017] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention uses pure ionic liquid as the extractant, completely eliminating the need to add water or organic diluents in traditional processes. This eliminates the problems of decreased product purity, solvent degradation, and high energy consumption in subsequent dehydration caused by the introduction of water. Moreover, it fully leverages the advantages of ionic liquids, such as high selectivity, high thermal stability, and low volatility, achieving a purity of >99.5% and a recovery rate of >99.8% for 1,3-butadiene while significantly reducing the overall energy consumption of the system.

[0018] 2. This invention, through the synergy of pure ionic liquids and optimized processes, systematically controls the reboiler temperature of key separation steps below 80°C, far lower than the high temperatures above 120°C in traditional NMP or acetonitrile processes. This low-temperature operating environment significantly reduces the residence time and thermal polymerization tendency of 1,3-butadiene in the high-temperature region, thereby avoiding equipment blockage and frequent maintenance problems, and significantly improving the long-term stability and reliability of the equipment.

[0019] 3. The integrated process design adopted in this invention simplifies the process structure and reduces the number of equipment and the load on the reboiler / condenser while achieving efficient separation of multiple components. The ionic liquid is almost non-volatile and can be completely recycled. After regeneration, its purity remains above 99.9%, with no wastewater or exhaust gas emissions, meeting the requirements of green chemical engineering and sustainable development. At the same time, it can reduce energy consumption by more than 30% compared with traditional processes. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A process flow diagram provided in an embodiment of this application is shown. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0023] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0024] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0025] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] To enable those skilled in the art to better understand this application, the following embodiments will be used to provide a detailed description of the anhydrous extractive distillation method for 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids provided in this application.

[0028] Example Example 1 This embodiment uses, as follows: Figure 1 The process apparatus and flow shown use steam cracking C4 fraction as raw material and a pure ionic liquid 1,3-dimethylimidazolium trifluoroacetate ([MMIM][TFA]) composed of 1,3-dimethylimidazolium cation and trifluoroacetic acid anion as extractant.

[0029] The C4 mixture has a feed flow rate of 10,000 kg / h and a mass composition of: 1,3-butadiene 52%, n-butane 7.82%, isobutane 3.64%, n-butene 6.5%, isobutene 24.03%, cis-2-butene 3.36%, and trans-2-butene 2.65%. It is a pure ionic liquid [MMIM][TFA], without the addition of any water or organic diluents.

[0030] The C4 mixture was preheated to 44°C and continuously fed from the 19th theoretical plate of the first extractive distillation column (1). The ionic liquid was preheated to 50°C and fed from the 3rd theoretical plate at the top of the column at a flow rate of 195.31 kmol / h.

[0031] The first extractive distillation column (1) is operated under the following conditions: top pressure 0.5 MPa, top temperature 45.94℃, bottom temperature 52.1℃, and reflux ratio 13.76. After the top vapor phase is condensed by the first condenser (10), part of it is refluxed and the other part is collected as alkane product with a flow rate of approximately 1142.62 kg / h, of which the sum of the purity of n-butane and isobutane is greater than 99.6%. Part of the first rich solvent obtained at the bottom of the column is used to provide rising steam through the first reboiler (13), and the other part is sent to the second extractive distillation column (2).

[0032] The first rich solvent from the bottom of the first extractive distillation column (1) is fed from the 27th theoretical plate of the second extractive distillation column (2). The ionic liquid, preheated to 50°C, is fed from the 2nd theoretical plate at the top of the column at a flow rate of 91 kmol / h.

[0033] The second extractive distillation column (2) is operated under the following conditions: top pressure 0.5 MPa, top temperature 44.94°C, bottom temperature 67.75°C, and reflux ratio 3.38 (falling within the range of 2-5 supported by claim 8). The vapor phase at the top of the column is condensed by the second condenser (11), with a portion refluxed and the other portion sent to the distillation column (3) as a butene mixture at a flow rate of approximately 3642.5 kg / h. A portion of the second rich solvent obtained at the bottom of the column is used to provide rising steam via the second reboiler (14), while the other portion is heated to 70°C by the heater (6) and then sent to the first solvent recovery tank (4).

[0034] The butene mixture from the top of the second extractive distillation column (2) is fed from the 56th theoretical plate of the distillation column (3).

[0035] The distillation column (3) was operated under the following conditions: top pressure 0.5 MPa, top temperature 42.5℃, bottom temperature approximately 53℃, and reflux ratio 6.09. The light component product (mainly n-butene and isobutene) was collected from the top of the column, with a combined purity of 99.5%; the heavy component product (mainly cis-2-butene and trans-2-butene) was collected from the bottom of the column, with a combined purity of 96.3%.

[0036] The second rich solvent is heated by heater (6) and then sent to the first solvent recovery tank (4). It undergoes a first flash evaporation at a pressure of 0.18 MPa to desorb most of the 1,3-butadiene. The material at the bottom of the tank enters the second solvent recovery tank (5) and undergoes a second flash evaporation at a pressure of 0.017 MPa to completely desorb the remaining 1,3-butadiene.

[0037] The 1,3-butadiene desorbed from the top of the first and second solvent recovery tanks is condensed by condensers (7) and (8) respectively, and then pressurized to 0.5 MPa by pumps (16) and (17) and mixed to obtain a 1,3-butadiene product with a purity of 99.59% and a recovery rate of 99.9%.

[0038] The ionic liquid regenerated at the bottom of the second solvent recovery tank (5) has a purity of 99.92%. After being cooled to 50°C by the condenser (9), it is pumped back to the top of the first extractive distillation column (1) and the second extractive distillation column (2) for reuse, thus realizing a closed-loop circulation of the solvent.

[0039] This embodiment fully demonstrates that by using the pure ionic liquid [MMIM][TFA] protected by the claims and the corresponding anhydrous extractive distillation process, 1,3-butadiene products with a purity higher than 99.5% and a recovery rate higher than 99.8% can be stably obtained at a temperature significantly lower than that of the acetonitrile extractive distillation process. At the same time, high-purity separation of alkanes and butenes and efficient regeneration and recycling of ionic liquids are achieved. The entire system operates stably and energy consumption is significantly reduced.

[0040] Example 2 This embodiment uses, as follows: Figure 1 The process apparatus and flow shown use C4 fraction from steam cracking as feedstock, and a pure ionic liquid, 1,3-dimethylpyridine bis(trifluoromethanesulfonyl)imide salt ([MMPY][NTF2]), composed of 1,3-dimethylpyridine cation and bis(trifluoromethanesulfonyl)imide anion, as the extractant. The C4 mixture was fed at a flow rate of 10,000 kg / h and had the following mass composition: 1,3-butadiene 52%, n-butane 7.82%, isobutane 3.64%, n-butene 6.5%, isobutene 24.03%, cis-2-butene 3.36%, and trans-2-butene 2.65%. The extractant was a pure ionic liquid [MMPY][NTF2], without the addition of any water or organic diluents.

[0041] The C4 mixture was preheated to approximately 44°C and continuously fed from the 33rd theoretical plate of the first extractive distillation column (1). The ionic liquid was preheated to 50°C and fed from the 4th theoretical plate at the top of the column at a flow rate of 180.61 kmol / h.

[0042] The first extractive distillation column (1) is operated under the following conditions: top pressure 0.5 MPa, top temperature 45.89℃, bottom temperature 47.89℃, and reflux ratio 15.45. After the top vapor phase is condensed by the first condenser (10), part of it is refluxed and the other part is collected as alkane product with a flow rate of approximately 1143.86 kg / h, of which the sum of the purity of n-butane and isobutane is 99.42%. Part of the first rich solvent obtained at the bottom of the column is used to provide rising steam through the first reboiler (13), and the other part is sent to the second extractive distillation column (2).

[0043] The first rich solvent from the bottom of the first extractive distillation column (1) is fed from the 51st theoretical plate of the second extractive distillation column (2). The ionic liquid, preheated to 50°C, is fed from the 3rd theoretical plate at the top of the column at a flow rate of 100.81 kmol / h.

[0044] The second extractive distillation column (2) is operated under the following conditions: top pressure 0.5 MPa, top temperature 44.93℃, bottom temperature 72.68℃, and reflux ratio 3.32. The vapor phase at the top of the column is condensed by the second condenser (11), with a portion refluxed and the other portion sent to the distillation column (3) as a butene mixture at a flow rate of approximately 3642.18 kg / h. A portion of the second rich solvent obtained at the bottom of the column is used as rising steam in the second reboiler (14), while the other portion is heated to 75℃ by the heater (6) and then sent to the first solvent recovery tank (4).

[0045] The butene mixture from the top of the second extractive distillation column (2) is fed from the 67th theoretical plate of the distillation column (3).

[0046] The distillation column (3) is operated under the following conditions: top pressure 0.5 MPa, top temperature 42.5℃, bottom temperature approximately 54℃, and reflux ratio of 6.

[0047] The light component products (mainly n-butene and isobutene) are collected from the top of the column, with a combined purity of 99.51% (meeting high purity requirements); the heavy component products (mainly cis-2-butene and trans-2-butene) are collected from the bottom of the column, with a combined purity of 96.5%.

[0048] The second rich solvent is heated by heater (6) and then sent to the first solvent recovery tank (4). It undergoes a first flash evaporation at a pressure of 0.183 MPa to desorb most of the 1,3-butadiene. The material at the bottom of the tank enters the second solvent recovery tank (5) and undergoes a second flash evaporation at a pressure of 0.01 MPa to completely desorb the remaining 1,3-butadiene.

[0049] The 1,3-butadiene desorbed from the top of the first and second solvent recovery tanks is condensed by condensers (7) and (8) respectively, and then pressurized to 0.5 MPa by pumps (16) and (17) and mixed to obtain a 1,3-butadiene product with a purity of 99.53% and a recovery rate of 99.8%.

[0050] The ionic liquid regenerated at the bottom of the second solvent recovery tank (5) has a purity of 99.96%. After being cooled to 50°C by the condenser (9), it is pumped back to the top of the first extractive distillation column (1) and the second extractive distillation column (2) for reuse, thus realizing a closed-loop circulation of the solvent.

[0051] This embodiment further confirms that by using another pure ionic liquid [MMPY][NTF2] protected by the claims and the same anhydrous extractive distillation process, 1,3-butadiene products with a purity higher than 99.5% and a recovery rate higher than 99.8% can be stably obtained at a temperature significantly lower than that of the acetonitrile extractive distillation process. It also achieves high-purity separation of alkanes and butenes and efficient regeneration of ionic liquids, which once again verifies the universality, efficiency and reliability of the process of the present invention.

[0052] Comparative Example To demonstrate the superiority of the anhydrous extractive distillation process based on pure ionic liquids described in this invention, this comparative example uses the widely adopted industrial acetonitrile (ACN) extractive distillation process as a control, comparing the processes under the same raw materials (composition as in Examples 1 and 2) and similar purity requirements for 1,3-butadiene products. Key operating parameters, performance indicators (Table 1), and energy consumption comparison (Table 2) are as follows: Table 1 Key performance indicators of [MMPY][NTF2], [MMIM][TFA] processes and acetonitrile method

[0053] Table 2. Energy consumption comparison between the [MMPY][NTF2] and [MMIM][TFA] processes and the acetonitrile method, based on an annual production of 10,000 tons of 1,3-butadiene.

[0054] Compared with the traditional acetonitrile method, the [MMPY][NTF2], [MMIM][TFA] process described in this invention has the following significant advantages while maintaining high product purity (>99.5%): The operating temperature was significantly reduced: the bottom temperature of the key extraction column was reduced by about 70-85°C, which effectively suppressed the thermal polymerization tendency of 1,3-butadiene from the source and greatly improved the stability of the unit operation.

[0055] The product recovery rate has been significantly improved: the recovery rate of 1,3-butadiene has increased from 95.33% to over 99.8%, reducing raw material loss and resulting in significant economic benefits.

[0056] Significantly reduced overall energy consumption: Due to the elimination of the need for water addition, low operating temperature, and high solvent selectivity, the total energy consumption of the system is reduced by 30.6% to 44.3%, demonstrating outstanding energy-saving performance.

[0057] The process is green and simplified: it completely avoids the introduction of water and the resulting product pollution, solvent degradation and subsequent dehydration energy consumption problems, and achieves true anhydrous and environmentally friendly separation.

[0058] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0059] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0060] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0061] The above provides a detailed description of the anhydrous extraction and distillation method for 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and its core ideas. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An apparatus for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids, characterized in that, It includes a first extractive distillation column (1), a second extractive distillation column (2), a distillation column (3), a first solvent recovery tank (4), and a second solvent recovery tank (5) connected in sequence by pipelines; The first extractive distillation column (1) is equipped with an ionic liquid inlet and a C4 hydrocarbon mixture inlet; the top distillation pipeline of the first extractive distillation column (1) is connected to the first condenser (10); the first condenser (10) is equipped with a product collection pipeline and a reflux pipeline to the first extractive distillation column (1); the bottom of the first extractive distillation column (1) is equipped with a solvent-rich outlet pipeline, one of which is connected to the first reboiler (13) and the other is connected to the feed inlet of the second extractive distillation column (2); The second extractive distillation column (2) is provided with an ionic liquid feed inlet and a rich solvent feed inlet from the first extractive distillation column (1); the distillate pipe at the top of the second extractive distillation column (2) is connected to the feed inlet of the distillation column (3) via the second condenser (11); the bottom of the second extractive distillation column (2) is provided with a rich solvent outlet pipe, one of which flows back to the second extractive distillation column (2) via the second reboiler (14), and the other of which is connected to the feed inlet of the first solvent recovery tank (4) via the heater (6); The distillation column (3) has a top distillation line connected to the outlet line and the reflux line returning to the distillation column (3) via the third condenser (12); the bottom of the distillation column (3) has an outlet line, one of which is the product outlet and the other is returned to the distillation column (3) via the third reboiler (15). The top gas phase outlet of the first solvent recovery tank (4) is connected to the first 1,3-butadiene collection pipeline via the fourth condenser (7) and then via the pump (16); the bottom liquid phase outlet of the first solvent recovery tank (4) is connected to the inlet of the second solvent recovery tank (5); The top gas phase outlet of the second solvent recovery tank (5) is connected to the second 1,3-butadiene collection pipeline via the fifth condenser (8) and then via the pump (17); the bottom liquid phase outlet of the second solvent recovery tank (5) is connected to the ionic liquid inlet of the first extractive distillation column (1) and the second extractive distillation column (2) via the pump (18) and then via the sixth condenser (9), forming an ionic liquid closed-loop circulation loop.

2. A method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids, characterized in that, Includes the following steps: S1: After the C4 hydrocarbon mixture and ionic liquid are preheated, they are continuously fed into the first extractive distillation column (1) for the first stage of extractive distillation. Alkane products are separated from the top of the first extractive distillation column (1), and 1,3-butadiene is obtained from the bottom of the column. S2: The first rich solvent and ionic liquid obtained from S1 are fed into the second extractive distillation column (2) for a second extractive distillation. The butene mixture is separated from the top of the second extractive distillation column (2), and the second rich solvent rich in 1,3-butadiene is obtained from the bottom of the column. S3: The S2 butene mixture is fed into a distillation column (3) for distillation separation. The light component butene product is collected from the top of the distillation column (3), and the heavy component butene product is collected from the bottom of the column. S4: After heating the second rich solvent, it is sequentially introduced into the first solvent recovery tank (4) and the second solvent recovery tank (5) for two-stage pressure reduction flash evaporation to recover the desorbed 1,3-butadiene. The products are then combined to obtain the 1,3-butadiene product. S5: After the pure ionic liquid after removing 1,3-butadiene from the bottom of the second solvent recovery tank (5) is cooled, it is circulated to the top of the first extractive distillation column (1) and the second extractive distillation tank (2) for reuse.

3. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The ionic liquid contains no water or diluent.

4. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The cation of the ionic liquid is an imidazole or pyridine cation.

5. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The anion of the ionic liquid is trifluoroacetate or bis(trifluoromethanesulfonyl)imide.

6. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The C4 hydrocarbon mixture is preheated to 42°C~45°C; the ionic liquid is preheated to 49°C~50°C.

7. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The first extractive distillation column (1) in S1 has 55 to 90 trays. The C4 hydrocarbon mixture inlet is located in the range of the 30th to 50th tray from the top, and the ionic liquid inlet is located in the range of the 2nd to 4th tray from the top. The top pressure of the first extractive distillation column (1) is set to 0.5 to 0.55 MPa, the top temperature is 45 to 47°C, and the bottom temperature is 48 to 53°C.

8. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The second extractive distillation column (2) in S2 has 60 to 85 trays. The C4 hydrocarbon mixture inlet is located in the range of the 45th to 55th tray from the top, and the ionic liquid inlet is located in the range of the 2nd to 4th tray from the top. The top pressure of the second extractive distillation column (2) is set to 0.5 to 0.55 MPa, the top temperature is 43 to 48°C, and the bottom temperature is 65 to 80°C.

9. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The distillation column (3) in S3 has 80 to 100 trays; the butene mixture feed inlet is located in the range of the 60th to 70th tray from the top; the top pressure of the distillation column (3) is set to 0.5 to 0.55 MPa, the top temperature is 42 to 45°C, and the bottom temperature is 51 to 54°C.

10. The method for anhydrous extractive distillation of 1,3-butadiene in C4 hydrocarbons based on pure ionic liquids according to claim 2, characterized in that, The S4 process involves two stages of pressure reduction flash evaporation. The first flash evaporation pressure is 0.15~0.20 MPa, and the second flash evaporation pressure is 0.01~0.05 MPa.

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